Multiple Sclerosis (MS) is a debilitating autoimmune neurological disease. Th17 cells have emerged as key drivers of pathogenesis in chronic autoimmune disease and are increased in MS patients. Th17 cells are also critical for driving CNS inflammation in the murine model of MS, experimental autoimmune encephalomyelitis (EAE). Our previous work demonstrated that Th17 cells are dependent on signals from IL-23 for their proliferation and differentiation into effector cells capable of driving inflammation in EAE. Although Th17 cells are mostly considered as IL-17 producers, they have many additional functions and IL-17 is not always sufficient to drive disease. However, IL-23 is critical, and our goal is to understand the specific mechanisms by which IL-23 promotes Th17 functions in inflammatory disease. We have recently discovered a novel integrin that is expressed by effector Th17 cells in an IL-23-dependent manner, and required for EAE. Published reports describe increased expression of this integrin in a number of human inflammatory diseases, including MS. However, almost nothing is known about its functional importance in T cells, and in particular Th17 cells. Collectively, these data form the basis for our central hypothesis that this integrin is a key IL-23-driven molecule involved in determining the inflammatory activity of autoimmune Th17 cells. We now aim to interrogate the role of its expression in Th17-mediated inflammation, and thereby to validate this integrin as a novel Th17-directed therapeutic target.